BISC 208 Exam 2

Invertebrates

Animals without a backbone

What is the percentage of invertebrates out of all the animal species

Makes up more than 95% of all animal species

Phylum Porifera

Sponges

What are the characteristics of sponges

Have lost their germ layers and lack true tissues

Spongocoel

Drawn in through pores into a central cavity

where does the water flows out

Through the osculum, a large opening at the top

Most cnidarians exist in two body forms

Sessile polyp or motile medusa

What does the polyp form looks like

Has a tubular body with an opening at the top end surrounded by tentacles

What does the medusa form looks like

Free swimming, has an umbrella shaped body

What does cnidarians consist of

Stinging cells called cnidocytes which function in defense or capture of prey

What does cnidocytes contain

Nematocyts, powerful capsules with an inverted coiled and barbed thread,

What helps with the discharge of nematocyts

Hair-like structures called cnidocil, detect chemical stimulus and lead to discharge

How does cnidarians attack and kill its prey

The filament penetrated the prey, injecting a small amount of toxin causing it to get immobilized and passed into the mouth by the tentacles

Lophotrochozoa is a clade that consists of the following phyla

1. Platyhelminthes

2. Rotifera

3. Bryozoa

4. Brachiopoda

5. Mollusca

6. Annelida

Platyhelminthes or flatworms, have three distinctive embryonic germ layers

Triploblastic

What does platyhelminthes lack of

A coelom, are considered acoelomates

What are characteristics of Platyhelminthes

Contain only one opening that serves as both mouth and anus, they are bilaterally symmetrical

Phylum rotifera characteristics

• pseudocoelomates

• Separate opening for mouth and sinus

mouth opens into a circular, muscular pharynx called

A mastax

Rotifera’s reproduction

Unfertilized diploid eggs develop into females by parthenogenesis

One common feature of mollusca

Soft body which in many species is found under a protective external shell

Mollusca body plan

• a muscular foot used for movement

• A visceral mass, containing internal organs

• A mantle, which secretes a shell

Mollusca have an open circulatory system with a heart that pumps a body fluid called

Hemolymph

Mollusca have Specialized excretory organ called

Metanephridia which removes nitrogenous and other wastes

What does the mouth of a mollusk may contain

A radula, a protrusible, tongue-like organ that is used for eating plants or boring into shells of other species

What are Annelids

A large phylum that consists of segmented worms including free-ranging marine worms, tube worms, earthworms and leeches

Annelids show segmentation which has 3 advantages

1. Components of the body are repeated in each segment. If components in one segment fails the other segments will still function

2. The fluid filled coelom acts as a hydrostatic skeleton, muscle contractions are minimized in segmented animals allowing for effective locomotion over solid surfaces

3. Segmentation permits specialization of some segments for specialized functions

What does all annelids except leeches have

Chitinous bristles called setae on each segment, in some annelids the setae are situated on a fleshy, footlike parapodia that helps with movement

Nervous system of annelids

Have a comparatively advanced nervous system with cerebral ganglia and a large ventral nerve cord that runs down the length of the body

How is the annelids circulatory system

Circulatory system is closed, respiration occurs directly through the skin surface which restricts them to moist environments

Annelids’ digestive system

Complete with specialized regions: mouth, pharynx, esophagus, crop, gizzard, intestine and anus

What are phylum nematoda

Also called roundworms are small thin worms that range in size from less than 1mm to 5 cm

Where are nematoda found in

All types of habitats and some of them are parasitic in nature

What are their body covered in

A tough cuticle made primarily of collagen (a structural protein)

What are nematoda

Pseudocoelomates which functions as a skeleton and circulatory system

Characteristics of Nematoda

• Have complete digestive system composed of a mouth, pharynx, intestine and anus

• Fertilization taking place internally

Arthropoda

Arthropods are the most diverse phylum on earth and include organisms like spiders, insects, and crustaceans

Features that make arthropods so successful

Exoskeleton, segmentation and jointed appendages

What is the body of arthropod covered by

A hard cuticle, an exoskeleton made up of chitin and protein

What is the function of the exoskeleton

Impermeable to water, which may have enabled arthropods to conserve water and colonize land ( similar to tough seed coat in plants allowing them to colonize land)

Arthropods are segmented

Many of the segments bear jointed appendages

What do jointed appendages permit

Complex movements and functions such as walking, swimming, sensing, breathing, food handling and reproduction

Phylum arthropoda body plan

Arthropods have a well-defined head, which includes a brain consisting of cerebral ganglia connected to smaller ventral nerve ganglia

Ommatidia

Arthropods have compound eyes composed of independent visual units

Tough cuticle does not allow diffusion of gases, they require special organs for gas exchange:

Aquatic arthropods have feathery gills, terrestrial arthropods have a highly developed tracheal system

What are Deuterostomes

Grouped together because they share similarities in patterns of development

striking feature of phylum echinodermata

Is their modified radial symmetry

Characteristic of echinodermata

There is no brain and only a simple nervous system consisting of central nerve ring with radial branches to each limb

Radial symmetry is present only in adults

Free swimming larvae have bilateral symmetry and metamorphose into the radial symmetrical adult form

What are echinodermata

Coelomates and portion of the coelom is adapted into a water vascular system: a network of canals that branch into tiny tube feet that function in movement, gas exchange, feeding and excretion

Four critical innovations in the body plan of chordates that distinguish them from other animals

1. Notochord

2. Dorsal hollow nerve cord

3. Pharyngeal slits

4. Postanal tail

Notochord

A single flexible rod that lies between the digestive tract and nerve cord. Composed of fibrous tissue the notochord is stiff yet flexible and provides skeletal support

Dorsal hollow nerve cord

Solid tube that lies ventral to the alimentary canal. In vertebrates this cord develops into the brain and spinal cord

Pharyngeal slits

Slits close to the mouth region where water enters through the mouth and exits through the slits. They function as filter-feeding devices and may develop into gills for gas exchange

Postanal tail

In aquatic chordates this tail is used for locomotion

What is an animal

Animals are multicellular eukaryotes (animal cells lack cell walls)

Animal use ingestion, the eating of food

• Fungi absorb nutrients after digesting food outside their body

• Heterotrophs

Nearly all animals reproduce sexually

Adults are diploid, gametes are haploid, and fuse to form a diploid zygote

Broad differences in animal phyla

1. Types of body symmetry

2. Number of germ layers

3. Features of embryonic development

Types of body symmetry

Can be radial, bilateral, or no symmetry

Blastula

Zygote divides by mitosis to form a hollow ball of cells

Germ layers

One side of the blastula folds in and the cells rearrange to form a gastrula with three embryonic layers

Endoderm

Forms a lining of the future digestive tract

Ectoderm

Forms an outer layer that will give rise to the skin and nervous system

Mesoderm

Forms a middle layer that will give rise to muscles and most internal organs

Some animals are diploblastic

Two layers, Ectoderm (outer layer) and endoderm (inner layer)

Most animals are triploblastic

Three layers, protostome and deuterostome

During the process of gqstrulqtion, the endoderm forms an opening

Blastopore

Protostomes

Blastopore forms the mouth

Deuterostomes

Blastopore forms the anus, mouth forms later

Morphological differences in bilateria

Body cavity → space that houses internal organs

Coelom

Fluid filled body cavity

Coelomates

Contain true body cavity

Pseudocoelomates

Coelom is not completely lined with tissue

Acoelomates

Lack a fluid filled cavity.

Segmentation

Body is divided into regions called segments

Advantage of segmentation

It allows specialization of body regions.

Vertebrates characteristics

Retain the characteristics of chordates as well as some additional traits

Vertebral column

The notochord is replaced by a bony or cartilaginous column of interlocking vertebrae

Cranium

Anterior end of the nerve cord forms a well-developed brain enclosed in a protective bony or cartilaginous cranium

Endoskeleton of cartilage or bone

The endoskeleton provides structural support and is composed of either bone or cartilage

Cyclostomata

Jawless fishes

Hagfish

Marine cyclostomes that lack eyes, jaws, fins and even vertebrae

What does hagfish skeleton consist of

Largely of a notochord and a cartilaginous skull that encloses the brain

Lampreys

Similar to hagfish, lack a hinged jaw and true appendages

What do lamprey possess

A notochord surrounded by a cartilaginous rod that represents a rudimentary vertebral column

Gnathostomes

Jawed vertebrates

Gnathostomes

All vertebrate species that possess jaws

Hinged jaw

An important evolutionary development that led to great diversification of vertebrates

Where did hinged jaws evolved D from

From gill arches, cartilaginous or bony rods that help to support gills.

Chondrichthyans

Cartilaginous fish

Cartilaginous fishes

Their skeleton is composed of flexible cartilage

Why do they sink?

Are denser than water which means that they will sink if they stop swimming

Heart of chondrichthyans

Consists of 2 chambers, an atrium and a ventricle

Cartilaginous fishes circulation

Employ single circulation, blood is pumped from heart to capillaries in the gills to collect oxygen and then back to the heart

Osteichthyans

Bony fish

In actinopterygii, or ray finned fishes

The fins are supported by thin, bony, flexible rays and are moved by interior muscles

Examples of actinopterygii

Lionfish, morey eels, sea dragons, cold and salmon

In sarcopterygii or lobe-finned fishes

The fins are supported by skeletal extensions and are moved by muscles within the fins

Examples of sarcopterygii

Coelacanth and Australian lungfish